Reciprocating motion control device

ABSTRACT

The novel control device is adapted to be attached to a sewing machine having a rotary drive means driving a vertical needle bar mounted for reciprocation between an upper and lower position with respect to a looper located below the needle. The machine has a transmission system operably connected between the rotary drive means and the needle bar. The transmission system includes a lever pivotably mounted between its ends and pin connected at one end to the needle bar. The other end is connected to a crank on the rotary drive means through a pitman that is pin connected therebetween. In addition, the crank is operably connected to a looper for synchronously driving the looper with the needle bar. The transmission system also includes the control device in the form of two pin-connected links connected between a fixed pivot point and the pin connection of the crank and the pitman. Means are provided to pivot the respective link about the fixed point between two positions, one of which allows the lever to idle. On this respective link is formed a cam that cooperates with a lug on the lever that prevents the respective link to move from the first to the second position unless the needle bar is in its upper position.

United States Patent 1 1 1111 3,866,478

McKeen 1 Feb. 18, 1975 [5 RECIPROCATING MOTION CONTROL a sewing machinehaving a rotary drive means driving DEVICE a vertical needle bar mountedfor reciprocation between an upper and lower position with respect to a[76] Invfimor' fi ";,:;b S Mamie looper located below the needle. Themachine has a transmission system operably connected between the [22]Filed: Nov. 21, 1972 rotary drive means and the needle bar. Thetransmission system includes a lever pivotably mounted be- [211 Appl'308390 tween its ends and pin connected at one end to the needle bar.The other end is connected to a crank on [52] US. Cl. 74/40, 112/219 R,112/221 the rotary drive means through a pitman that is pin [51] Int. ClFl6h 21/32, D05b 69/22 connected therebetween. In addition, the crank isop- [58] Field of Search 112/219 R, 219 B, 220, erably connected to alooper for synchronously driv- 112/221, 67; 74/40, 41, 42 ing the looperwith the needle bar. The transmission system also includes the controldevice in the form of [56] References Cited two pin'connected linksconnected between a fixed UNITED STATES PATENTS pivot point and the pinconnection of the crank and 2 560 750 W195 Roucka et al M 74/40 thepitman. Means are provided to pivot the respec- 3688713 9/1972 McKee112/219 R tive link about the fixed point between two positions,3,688,715 9/1972 McKeen 112/219 R one of which allows the lever toidlethis p tive link is formed a cam that cooperates with a lug on thelever that prevents the respective link to move from the first to thesecond position unless the needle bar is in its upper position.

Primary Examinerl'l. Hampton Hunter Attorney. Agent, or Firm-DominickNardelli [57] ABSTRACT The novel control device is adapted to beattached to 2 Clams 2 Drawing Figures RECIPROCATING MOTION CONTROLDEVICE FIELD OF THE INVENTION This invention relates to a means forstopping reciprocating motion of a work element, and more particularlyto means for stopping a work element in a predetermined position.

BACKGROUND OF THE INVENTION In the art of automatic operations,particularly in the garment industry using conventional sewing machines,it is often necessary to position the sewing needle in an up positionwith respect to the sewing surface and looper. The up position isrequired when the operator wishes to remove the work or to makenecessary thread adjustments and to lock the thread to itself to preventunravelling. Usually, the needle bar would not end up in a desired upposition and the operator, with conventional machines, is required tomanually adjust the machine to raise the needle bar to the desiredposition by turning the flywheel of the sewing machine. This relativelyslow, manual adjustment consumes a great deal of the operators time andsubstantially increases the cost of the article being manufactured. Theprior art teaches to eliminate the manual adjustment of the sewingmachine by utilizing automatic or semi-automatic mechanical orelectrical stop motion devices with sew ing machines. However, most ofthe previously proposed devices are of substantially complexconstruction, requiring extensive modifications of the sewing machineitself, and in some cases are suitable only for particular types ofsewing machines. A number of such previously proposed devices usesauxiliary motors and clutches to rotate the flywheel of the sewingmachine to the proper position. Other devices utilize electronic controlcircuits for the drive motor of the sewing machine or for engaging anddisengaging pawls and earns attach to the drive shaft of the sewingmachine. Still other previously proposed devices which have beenutilized in the field are relatively expensive and complicated inconstruction. Further, the sewing machine utilizes cams and pawls intheir stop motion devices which produces excessive shock to the machineswhich often results in breakage, distortion and undue wear of the parts.

OBJECT OF THE INVENTION An object of this invention is to provide ameans for stopping the reciprocating motion to a tool at a predeterminedpoint.

Another object is to provide a simple, dependable means for stopping areciprocating motion of a tool at a predetermined point.

Another object is to provide a means for stopping reciprocating motionof a tool at a predetermined point, without developing excessive shockand jarring of the machine parts.

These and other objects and features of advantage will become moreapparent after studying the following description of the preferredembodiment in conjunction with the appended drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side section elevation ofasewing machine schematically showing the internal, mechanical link 5ages with the novel stopping means positioned during reciprocation ofthe needle bar.

FIG. 2 is also a side section elevation of the machine in FIG. I withthe novel stopping means positioned while the needle bar is stopped inthe up position.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to the drawing, there isshown schematically a showing machine 10, embodying the novel means ofthe present invention. Machine has a housing 12 which encloses anelectric motor 14 that provides power to the sewing machine toreciprocate a vertically disposed needle bar 16 during the sewingoperation, through a standard transmission system 18. The system 18,besides reciprocating the needle bar up and down, also actuates a looper24 synchronous with the needle 26 on the end of bar 16. To provide loopstitching as is common in the art. The system 18 includes a flywheelrotated by the motor 14 about an axis normal to the drawing. To theflywheel 20 is connected a crank arm 28 by a pin 30. A pitman 34 isconnected at one end to arm 28 by a pin 32, and at the other end to oneend of a lever arm 36 by pin 40. The lever arm 36 rocks about astationary pin 37, located between its end and has the other end pinconnected to a link 35 that is in turn pin connected to the needle bar16. Thus, as motor 14 rotates the flywheel 20, the lever arm 36 isrocked up and down about pin 37 and the needle arm 16 and needle 26reciprocate up and down in the plane of the drawing.

To actuate the looper 24 synchronous with the needle 26 an extension arm72 is integrally formed to the pitman 34, substantially as shown, andhas its upper end connected to a transmission link 76 by a pivot pin 74.The link 76 depends from pin 74 and has its lower end connected to acrank arm 80 by a pivot pin 78. The link 76 is shown broken away to showthe details behind the link 76. The arm 80 is disposed to rotate about afixed shaft 79 and has, integral therewith, a bevel gear 77. Anotherbevel gear 61 measures with gear 77 to provide reciprocating, rotationalmotion to a transmission shaft 62 that is suitably joumaled within thehousing 12 to rotate about its own axis. The looper 24 is connected tothe opposite end of shaft 62. The description of the transmission system18, up to this point, is standard in the art.

The novel means that allows the pitman 34 to reciprocate the needle baror to stop the needle bar 16 while the motor 14 keeps running will nowbe explained. To reciprocate the lever arm 36, the line of thrust of thepitman should be substantially perpendicular to the arm 36 and thereforepitman 34 should be substantially perpendicular to arm 36. The pitman isheld in this position by a control linkage that includes a controlledlever 52 pin connected to the housing 12 by a stationary pin 54 at oneend thereof. The lower end of lever 52 is pinconnected connected to acontrol link 55 by a pin 56. The other end of link 55 is pin-connectedto the pin 32. The control lever 52 is disposed in front of the leverarm 36 as viewed in the figures so that the lever 52 and arm 36 aremathematically in a skew position. The arm 36 preferably oscillates in aplane parallel to the control lever. The control lever 52 is held in itsfirst position, as shown in FIG. 1, by a connecting rod 57 extendingfrom the air piston and cylinder assembly 58. When pressure is appliedto assembly 58, the rod 57 is pulled to the left, as viewed in thedrawing, to swing the control lever 52 to the second position, as shownin FIG. 2. This causes the control link 55 to pivot with respect to thepitman 34 so that the pitman is no longer perpendicular to the lever arm36, thereby stopping its oscillation.

To insure that the pitman 34 and control link 55 are in the positionshown in FIG. 2, that is, parallel to each other so that the needle bar26 is in the up position, a cam 59 is conveniently mounted on thecontrol lever 52, while on lever arm 36 there is placed a lug 38, Thecam 59 is formed with a camming surface 60 that is cylindrically shaped,having its center at the axis of the pin 37 when the control lever 52 isin the first position as shown in FIG. 1. A space of a few thousandthsof an inch is between surface 60 and lug 38. The purpose of this spacingis that the lug 38 on lever arm 36 is free to oscillate up and downwithout friction therebetween while motor 14 is rotating with thecontrol lever 52 in the first position. To place the control lever 52 inits first position the air pressure is released for example from thepiston and cylinder assembly 58.

When the control lever 52 is moved from its first po sition to itssecond position, the needle bar 16 stops oscillating. As mentionedabove, this function is done by applying fluid pressure to assembly 58to pull the connecting rod 57 to the left. However, with the cammingsurface 60 on cam 59, and with lug 38 of lever arm 36, the control lever52 cannot move to its second position until lug 38 is free of thecamming surface 60, i.e., when in its down position. Thus surface 60 ismade so that it ends above lug 38 when the lug is in its lowestposition.

When the piston and cylinder assembly 58 is actuated to pull the controllever 52 to the left, to its second position, the lever 52 would notmove if needle bar is not in its up position because the lug 38 would bein the way of the camming surface 60. Only when the lug is below the cam59 could the control lever 52 move to its second position. Since thelength of the pitman 34 and the length of the control link 55 arepreferably the same, pins 40 and 56 will be aligned when the controllever 52 is in its second position. The control lever 54 is made with abight portion 52a to allow this align ment. This fixes the position ofboth pins 40 and 56 so that the pitman 34 only oscillates about pin 40as the motor 14 rotates. The cam 59 is provided with another surface 73that meets the surface 60 to form a point as shown. The function ofsurface 73 is to insure that the lug 38 slides down to and around thepoint when the control lever is being moved to its first position tostart sewing. Thus, the sewing machine is provided with a simple,inexpensive means for always stopping the needle 26 in its up position.

Although one embodiment of the invention has been shown and described,the invention is not to be considered limited to the disclosed,embodiment, for one skilled in the art, after studying this disclosure,could conceive other embodiments without departing from the spirit ofthe invention. Therefore, the invention is not limited to the disclosedembodiment but is limited to all embodiments, including those within thescope of the claims.

I claim:

1. In a device for converting rotary to reciprocating motion comprising:

a rotary drive means;

a work element mounted for reciprocation between first and secondlocations;

a lever arm pivotably mounted intermediate its ends and connected at oneend to said work element;

a crank arm pivotably connected at one end to said rotary drive means;

a pitman, pivotably connected between said crank and the other end ofsaid lever, to convert the rotary motion of said drive means to anoscillating motion on said lever arm;

a control lever pivotably mounted to said device and disposed to be skewwith said lever arm;

first means for selectively moving said control lever between a firstand second position;

a control link pivotably connected at one end to said control lever andat its other end to said crank arm at said point of connection betweenthe crank arm and said pitman; and

said control lever and said control link cooperating in said firstposition to hold the line of thrust of said pitman substantiallyperpendicular to said lever arm to oscillate it, and cooperating in saidsecond position, to hold the line of thrust of said pitman substantiallyin a line with said lever arm to hold it stationary;

the improvements comprising:

a lug formed on said lever arm and disposed between said other end ofsaid lever arm and its pivotal mount;

said control lever having a cam, with a cylindrical camming surfacedisposed to cooperate with said lug; and

said cylindrical camming surface having its center of curvature disposedat the pivotal mount of said lever arm and said surface extends adistance shorter than the arcuated travel path of said lug whenever thecontrol lever is in said first position.

2. In the device of claim 1 wherein:

said cam is limited to being elongated and fixed at one end to saidcontrol lever and disposed at an angle thereto so as to point towardsaid control link; and

said cam having a length such that when said lever arm is at one end ofits travel, said cam is capable of clearing said lug when said controllever is being moved by said first means from said first position tosaid second position.

1. In a device for converting rotary to reciprocating motion comprising:a rotary drive means; a work element mounted for reciprocation betweenfirst and second locations; a lever arm pivotably mounted intermediateits ends and connected at one end to said work element; a crank armpivotably connected at one end to said rotary drive means; a pitman,pivotably connected between said crank and the other end of said lever,to convert the rotary motion of said drive means to an oscillatingmotion on said lever arm; a control lever pivotably mounted to saiddEvice and disposed to be skew with said lever arm; first means forselectively moving said control lever between a first and secondposition; a control link pivotably connected at one end to said controllever and at its other end to said crank arm at said point of connectionbetween the crank arm and said pitman; and said control lever and saidcontrol link cooperating in said first position to hold the line ofthrust of said pitman substantially perpendicular to said lever arm tooscillate it, and cooperating in said second position, to hold the lineof thrust of said pitman substantially in a line with said lever arm tohold it stationary; the improvements comprising: a lug formed on saidlever arm and disposed between said other end of said lever arm and itspivotal mount; said control lever having a cam, with a cylindricalcamming surface disposed to cooperate with said lug; and saidcylindrical camming surface having its center of curvature disposed atthe pivotal mount of said lever arm and said surface extends a distanceshorter than the arcuated travel path of said lug whenever the controllever is in said first position.
 2. In the device of claim 1 wherein:said cam is limited to being elongated and fixed at one end to saidcontrol lever and disposed at an angle thereto so as to point towardsaid control link; and said cam having a length such that when saidlever arm is at one end of its travel, said cam is capable of clearingsaid lug when said control lever is being moved by said first means fromsaid first position to said second position.